In this paper,the relationship between additive particle size and the properties of AgSnO2 contact materials was studied.Bi2O3,TiO2 and CeO2 were chosen as additives,and four kinds of particle sizes were selected.Meanwhile, the proportion of additives was selected through wetting ability tests.And AgSnO2 contact materials are prepared by powder metallurgy technology.The physical and electrical contact properties of AgSnO2 contact materials doped with different kinds and particle sizes additive were studied,the results showed that the influence of particle sizes of three additives(Bi2O3,TiO2 and CeO2) on the properties of AgSnO2 contact materials is consistent,and fine additive particle is beneficial for the improvement of the properties of AgSnO2 contact materials.With the decrease of additive particle size, the physical and electrical contact properties of AgSnO2 contact materials are improved,and the optimal particle size of additive is 200nm.The results indicate that the properties of AgSnO2 contact materials can be improved by selecting the optimal particle size of additive.